1. Technical Field
The present invention relates to magnetoresistive transducers. More particularly, the present invention relates to a conductor configuration for dual stripe magnetoresistive transducers.
2. Description of the Prior Art
Continuing advances in magnetic media technology allow increasing data storage densities. One active area of development is that of reading and writing transducers. As such transducers are made smaller and smaller, data densities are increased. Magnetoresistive (MR) thin film technology has provided a particularly promising area of inquiry with regard to producing smaller reading and writing transducers. In such technology, MR conductive thin films, are formed into parallel stripes on a substrate using techniques analogous to those of the semiconductor arts. It is desirable to arrange the MR stripes as close together as possible to provide a narrow active region at a transducer air bearing surface. Dual stripe MR transducers, such as are described in U.S. Pat. No. 3,860,965, issued to Voegeli, and U.S. Pat. No. 3,879,760, issued to Lazzari, reflect the current state of the art.
Dual stripe magnetoresistive (MR) transducers require two sets of conductors to provide a supply of current for correctly biasing both MR stripes. The magnetic properties of ferromagnetic thin films used to produce MR transducers are strongly influenced by the topographical features of structures formed on a transducer substrate. Thus, the topography and arrangement of these conductors can affect the topography and spacing of the MR stripes. Topological effects result in different magnetic properties for each stripe. Thus, the noise characteristic for each stripe, referred to as Barkhausen noise, is different.
To provide an effective dual stripe MR transducer, ideally identical domain states should be present in each of the MR stripes. A transducer signal is typically a differential output of the two MR stripes. In this way Barkhausen noise in the two stripes should be largely cancelled through common mode rejection.
Approaches in prior art to providing a dual stripe MR transducer, for example as described by Kelley et al, IEEE Trans. Mag., MAG-17,6, November 1981 teach a transducer structure in which one MR stripe is flat. A second MR stripe which is provided is not flat. This difference is due to the shape of the conductors which are attached to the first stripe. This inconsistency in topography produces stripes having different magnetic properties. The resulting problem of Barkhausen noise is pronounced.
U.S. Pat. No. 3,879,760, is issued to Lazzari shows a conductor pattern which does not define the track edges. Rather, the MR stripes define the track edges. This configuration requires short MR stripes for small track widths and, therefore, is subject to multiple domains, which give rise to Barkhausen noise.
It has also been shown in the art (e.g. Lazzari) that if the two MR stripes in an MR transducer are arranged such that they are spaced apart by a large amount, then the two MR stripes exhibit similar topographies. This condition exists if the conductors for the first MR stripe are planarized. However, close coupling between the two stripes are then sacrificed and ideally identical domain state are unlikely.